This invention relates to combustion units and, in particular, to pulsating combustion units.
Pulsating combustion units are well known. One variety of pulse combustion units includes three geometrically-configured adjoining channels. There is an intake section, a combustion chamber and an exhaust channel or tail pipe. Fuel and air are injected through the intake channel into the combustion chamber where the mixture is ignited. The heat created by the combustion process generates a pressure wave which travels from the combustion chamber through the tail pipe, carrying with it various gases or effluents resulting from the combustion process.
As the effluent gases exit the tail pipe, and the exterior of the combustion chamber cools, a partial vacuum is created within the combustion chamber which, in turn, draws a new supply of air and fuel into the combustion chamber from the intake channel. This new fuel-air mixture is then compressed by the effluent returning or "pulsing back" from the tail pipe. The new mixture is ignited as a result of the pressure increase and the remaining heat within the combustion chamber, causing the entire process to repeat in a pulsing action.
Such units are described, for example, in my earlier U.S. Pat. Nos. 4,846,149 and 5,403,180.
One type of prior art unit includes space-apart plates. Typically the unit includes a restriction downstream of the intake end. In other words, the plates are spaced-apart closer together from the restriction to the exhaust end of the unit. A high heat transfer coefficient is realized from the pressure gain environment as the gases move through the narrowed channel and are compressed. However there is a limitation as to how much mass flow can be realized through the narrowed channel because of its decreased cross-section. This accordingly restricts the output of the unit. The unit could be upscale do a larger output by extending the length or by placing multiple units side by side. However, this may not be feasible due to space limitations.
Another problem with some prior art units has been a relatively high NO.sub.x in the exhaust. This has limited acceptance of such units due to environmental considerations.
Accordingly, it is an object of the invention to provide an improved pulsating combustion unit which overcomes disadvantages associated with the prior art.
More specifically, it is an object of the invention to provide an improved pulsating combustion unit which has a higher heat output compared to prior art units of equivalent size.
It is also an object of the invention to provide an improved pulsating combustion unit which is simpler and less expensive to fabricate compared to prior art units.
It is a still further object of the invention to provide an improved pulsating combustion unit which has lower NO.sub.x emissions compared to prior art units.